1. Field of the Invention
The invention resides in the field of chemical analysis instruments and more particularly relates to those devices which react a carrier gas with a volatilized liquid sample in the presence of a catalyst to produce a chemical change in the composition of the gas stream.
2. Description of the Prior Art
Chemical analysis instruments of the type for which the invention is intended are well known and described in the prior art. The function of these devices is to determine a particular composition of a substance by reacting within a reaction chamber a volatilized sample of the substance with a feed or carrier gas stream in a catalyst bed and then measuring one or more parameters of the reacted gas stream as an indicator of its composition.
A detailed description of such a device is found in U.S. Pat. No. 3,567,385, C. E. VanHall, in which an apparatus and method for determining total oxygen demand (TOD) of a substance is described. The oxygen demand of a material containing oxidizable components is determined by the combustion of a small sample of the material in a continuous stream of carbon dioxide within a heated catalyst bed. Carbon monoxide produced as a result of the combustion relates directly to the TOD of the sample which can thus be indirectly measured by a quantitative analysis of the reacted gas stream for carbon monoxide content. A particularly useful application of TOD measurement is the determination of pollution levels in water systems and waste streams. Other patents, such as U.S. Pat. Nos. 3,530,292, 3,560,156 and 3,840,341, which disclose apparatus and methods for measuring carbon or oxygen demand in liquid samples by the combustion method, may also utilize the present invention.
Since the measurements involved are quantitative, accuracy and reproductibility depend upon the physical characteristics and functional operation of the apparatus. Hence the size of the sample, particularly a liquid sample, and the rate of volatilization are among the critical parameters which must be closely controlled in order to provide meaningful measurements.
In accordance with this requirement, the present invention is directed toward a means for rapidly and completely volatilizing a liquid drop sample in a TOD or similar combustion analysis instrument.